(1) Field of the Invention
The present invention relates to the field of aircraft seats. It provides a bench having a plurality of seats for passengers of the aircraft.
(2) Description of Related Art
The bench is capable of withstanding a high level of deceleration to which the aircraft might be subjected, in particular in the event of a rough landing or of a crash, in order to provide the passenger(s) of the bench with protection.
The bench of the invention satisfies the requirements of regulations concerning rotorcraft seats and in particular the crashworthiness requirements.
Conventionally, aircraft seats or benches incorporate means for protecting the passenger(s) sitting on the seat or bench in the event of a crash. The term “passenger” is used to designate any person being transported on board the aircraft. Such protection means are commonly constituted firstly by the structure of the seat or bench, and secondly by one or more energy absorber devices.
Energy absorber devices are suitable for dissipating a fraction of the energy to which the seat or the bench is subjected in the event of a violent impact and/or a high level of deceleration, in particular during a crash. As a result, less energy is transmitted to the structure of the seat, and consequently to the passenger. The structure of the seat or bench is thus organized to absorb the stresses and limit the deformations induced by that energy and also to compensate for the deformation of the aircraft floor during a crash.
In a known embodiment, a seat has a leg assembly or “stand” and a “bucket” seat, itself comprising a seat proper and a back. The stand is anchored to the floor of the aircraft via four connection points and constitutes the structure of the seat to which the bucket is fastened.
With a bench, it is possible in the same manner to make use of a stand that is anchored via four connection points to the floor and on which there is fastened an assembly comprising a plurality of bucket seats. However, the bucket seats need to be connected rigidly to one another or else to the structure of the bench so as to be capable in particular of withstanding the stresses of a crash. The stand, constituting the structure of the bench, may be reinforced in order to provide such strength. By way of example, the bench may also have additional connection points with a vertical partition of the cabin of the aircraft.
Furthermore, document US 2006/0237586 describes a bench for a space vehicle. That bench is fastened to a frame that is connected via several connection points to the floor, to the ceiling, and to a vertical partition of the vehicle by means of bars. The tension in the bars is adjustable so as to enable the bench to have the same behavior and to provide the same protection in the event of an impact and regardless of its loading. The loading of the bench means the number and distribution of passengers on the bench together with their weights and sizes.
Also known is document EP 0 065 982, which describes a crashworthy seat for helicopters that includes an energy absorber device. The seat is secured to a support connected to a frame fastened to the floor of the helicopter. When the helicopter is subjected to a high level of deceleration, e.g. associated with a crash, the support moves relative to the frame by means of the energy absorber device. That device is made up, amongst other things, of wires that deform under the action of bending means. It is adjustable in order to adapt to the weight of the passenger of the seat, by modifying the number of wires that are deformed by the bending means.
Furthermore, document EP 0 099 677 describes an individual aircraft seat comprising a bucket seat having a back and a seat proper, a frame, vertical adjustment means, and a device for absorbing energy in the event of an impact. The frame comprises two parallel tubes and two pairs of collars connecting the tubes to the bucket seat. Each tube is connected to the floor of the aircraft via a pivot connection and to the ceiling of the aircraft either directly via a pivot connection or else via a connecting rod and pivot connections.
Also known is document U.S. Pat. No. 6,152,401, which describes a foldable aircraft seat having a back, a seat proper that can be folded relative to the back, a frame, and at least one device for absorbing energy in the event of an impact. The frame has two parallel tubes connected to the back and each comprising two telescopic tubes. Each telescopic tube enables the frame to be connected respectively to the floor of the aircraft via a pivot connection and to the ceiling of the aircraft via a transverse tube and two pivot connections.
Furthermore, document DE 10 2007/011962 describes an aircraft seat having a seat proper and a frame including two vertical retention elements. Each vertical element is fastened to the floor and to the ceiling of the aircraft and supports the seat proper via two belts.
In addition, document FR 2 389 045 describes an energy absorber device and seats including at least one such energy absorber device. For example, a seat has a first energy absorber device fastened to the back of the seat and connected by a cable to the ceiling of the aircraft, and also a second energy absorber device fastened to the seat proper of the seat and to the floor of the aircraft. Another seat has a first energy absorber device fastened to the frame of the seat and connected to its seat proper together with a second energy absorber device fastened to the seat proper and to the floor of the aircraft.
Finally, document FR 2 962 714 describes a foldable aircraft seat having a back and a movable seat proper together with a frame. The frame includes a vertical portion in which the seat proper and the back are stored. The seat proper and the back are movable relative to the frame, both in rotation and in translation, with two pairs of connecting rods connecting the seat proper with the back and also connecting the seat proper with the frame.
As mentioned above, a seat and a bench may have architecture of the same type, with a stand constituting the structure of the seat or the bench, and having one or more bucket seats fastened thereto. The discussion below begins by being restricted to a seat, but the conclusions are substantially identical for a bench.
During a crash, a seat must be structured to absorb the energy resulting from the high level of deceleration of the aircraft and to compensate for deformation of the cabin floor and of the seat and also to compensate for the stresses to which the seat is subjected.
Firstly, the deformation of the floor is a function of the direction and the magnitude of the impact to which the aircraft is subjected. Such deformation can therefore be determined accurately for particular circumstances involving well-defined crashes.
However, in practice, the way a crash happens is not well-defined and might lead to any deformation of the aircraft floor. The stand of the seat must therefore be structured to compensate for such deformation of the floor in order to limit the effect it has on the structure of the seat. The deformation of the floor leads to deformation between the connections of the stand on the floor, thereby stressing the stand as a whole. The effects of such stresses on the passenger of the seat still need to be limited.
Consequently, the stand of the seat is dimensioned to take account of the deformation of the floor and of the internal stresses on the seat that result therefrom during a crash of any kind. As a result, the stand of the seat is of large dimensions and constitutes a major fraction of the weight of the seat.
Furthermore, since the aircraft is subjected to a sudden and strong deceleration, the seat needs to be organized to preserve the passenger. An energy absorber device may be incorporated in the seat in order to dissipate a fraction of the energy that results from this deceleration. By way of example, the device may be interposed between the stand and the bucket seat, with the bucket seat being capable of sliding relative to the stand beyond a certain level of force corresponding to a certain level of deceleration.
Such an energy absorber device is described in document FR 2 930 613, with document FR 2 930 520 describing a seat fitted with such a device.
Such a device generally includes deformable holder means such that the bucket seat is held firmly in a normal use situation. In the event of a crash, the strong deceleration to which the aircraft is subjected causes the holder means to be deformed and thus leads to the bucket seat sliding downwards relative to the stand. As a result, the fraction of the energy to which the seat is subjected during the crash is dissipated in deforming the holder means. The energy absorber device is then said to have been deployed, meaning that those holder means have been deformed during a crash.
Furthermore, there are additional requirements that need to be taken into account when designing and selecting a seat.
Firstly, the size of the seat should be reduced to a minimum in order to make it easier to install in the cabin of the aircraft, in particular in order to optimize the number of seats that can be installed in the cabin. Furthermore, reducing this size serves to limit inconvenience for passengers sitting on neighboring seats, in particular by leaving room for passing the feet of the passenger situated immediately behind the seat in question. On this topic, the stand of a seat with four connection points is very penalizing.
Furthermore, small seat size also makes it easier to arrange spaces in the cabin for moving about and for storage. The space occupied by the seat remains considerable even when it is not in use, thereby leading to wasted space in the cabin. Solutions exist for folding the seat proper up against the back in order to release some space, but the stand continues to be penalizing, since the floor area it occupies remains unchanged.
Finally, the structure of the seat needs to be as simple as possible in order to limit its weight and the cost of fabricating it. In addition, low weight also makes the seat easier to handle when changing the seat layout in a cabin.
A seat that complies with regulations nowadays has a weight of more than 10 kilograms (kg) and recent developments do not make it possible to obtain a weight of less than 10 kg. For a bench, an equivalent weight is obtained depending on the number of seats, i.e. more than 10 kg per seat.